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000
FXUS63 KTOP 060007
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
607 PM CST Thu Dec 5 2013

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 207 PM CST THU DEC 5 2013

Mid level shortwave responsible for the chance of snow tonight is
currently located over NM and is forecast to lift northeast across
KS. Mid level lift increases ahead of the approaching shortwave
later this evening allowing snow to develop aloft. The snow may have
trouble reaching the ground as forecast soundings show rather dry
air in the lower levels it will have to overcome. Short term models
continue to show reflectivity spreading into the area from SW KS
later this evening which may only amount to flurries especially
along and south of interstate 70. After 06z tonight as the shortwave
passes more wide spread snow begins to develop across SE KS with the
best chances remaining along and south of interstate 35. Behind the
wave another reinforcing shot of cold air advects drier air into the
region from the north tomorrow morning also limiting the northern
extent of the snow. The snow should tapper off for the southeast
counties around mid day tomorrow with totals ranging from a dusting
to one inch. The 12z MOS guidance was much colder overnight than
previously expected therefore have lowered temperatures a few
degrees for tonight. Although given the cold air mass and snow cover
located over northern NE this seemed reasonable. Decided not to go
as low as MOS guidance given that cloud cover may moderate temps and
the winds keep the boundary layer mixed, both limiting any
enhancement from radiational cooling. Ultimately, think low
temperatures tonight will range from near zero in north central KS
to the low 10s in east central KS. Wind gusts will pick up overnight
to around 20 mph as the wave moves across the region which will
bring wind chill values down into the -0s to -10s by sunrise. The
clouds will continue to hang around most of tomorrow morning but
begin to clear out during the afternoon and evening hours. High
temperatures tomorrow will remain in the mid 10s to near 20 as the
cold air continues to filter into the region from the north with
wind chills in the 0s.

.LONG TERM...(Friday Night through Thursday)
Issued at 207 PM CST THU DEC 5 2013

Fri night-Sat night:  Cold high pressure continues to move
southward into our area Friday night into Saturday morning.
Current temperatures under this high currently up over southern
Canada are in the negative teens. Despite moderation as it moves
southward, with clearing skies have gone on the cold side of
guidance with lows -3 in the NW to about 4 above in the southeast.
Clouds on the increase from the west through the day Saturday will
also hinder a warmup and have gone on the cool side for highs with
18-21 across the area which may still be too high. Expect
temperature to then stall a bit for the night Saturday night as
clouds and chances for snow move in from the west.

Sunday/Monday:  Upper trof moving in for Sunday is also driven by
phasing with smaller and larger scale trofs to the north, and
guidance suggest a leading ripple of energy to cross the cwa
overnight before energy rotates out of the base of the larger trof
and over the forecast area Sunday afternoon and evening. Not a
tremendous amount of moisture for this system to work with, but
what comes in with the system and is able to interact with the
dynamics looks to be enough to produce generally 2-4 inches of
snow across our area. Northwest zones progged to get a few inches
with the first wave evening to early morning hours, with the
remainder of the area getting a few inches overnight into Sunday.
Far SE counties soundings suggest drying out in the mid levels,
but appears to be enough cold air down low to counter freezing
drizzle changeover chances, and just will carry a snow or freezing
drizzle wording across the farthest SE areas. Frontogenetic
forcing doesn`t align with instability in the column this far
north, but rather snowfall appears driven by the frontogenesis /
qvector convergence moving through with the waves, and banded
heavy snow is not anticipated. Highs in the 20s forecast for
Sunday. Incoming colder air behind the passing wave drops
overnight lows Sunday night back into the single digits to low
teens, with teens for highs on Monday.

Tues-Thurs: Tuesday and Wed both GFS and EC slowly take the upper
trof across the area with temperatures only making slight
improvements through this period. Thursday may bring either more
zonal flow or a ridge aloft over the state and may moderate
temperatures a few degrees higher for Thursday but a bit far out
to be too optimistic.

&&

.AVIATION...(For the 00Z TAFs through 00Z Friday Evening)
Issued at 604 PM CST THU DEC 5 2013

VFR cigs expected through the period. Some light flurries are
possible at MHK,TOP and FOE but did not include as a visibility
restriction at this time. Winds continue from the north around 10
kts with some gusts to around 18 kts.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Sanders
LONG TERM...67
AVIATION...53